1. Field of the Invention
This invention relates to mixing devices. More particularly, this invention relates to a new and improved apparatus and method for making a multi-portion mixing element for a static mixer, a multi-portion mixing element for a static mixer, and a static mixer including a multi-portion mixing element.
2. Prior Art
Many polymerizable resins are used in multi-component dispensers where final mixing of the resin takes place in the disposable tip called a static mixer. One of the more common static mixer designs utilized today is the twisted ribbon or the two-paddle mixer. These stationary mixers rotate the fluid resin components 180xc2x0, then split each component in half. The fluid components go through a series of splits and blends until the desired mixing is achieved. The dual component, single fluid resin then exits the static mixer and is deposited as required. When use of the resin applicator is complete, the static mixer tip is disposed of and the multi-component dispenser can be used another day with a new mixing tip. Examples of such devices are found in U.S. Pat. No. 4,538,920 and U.S. Pat. No. 4,753,536.
Although the twisted ribbon mixer is quite reliable and inexpensive, it does have drawbacks. Resin components with large viscosity differences are difficult to blend. Since many of the multi-component dispensers are hand operated, highly viscous fluids cannot be blended by hand because of the back pressure developed during the circuitous route the resin blend must take in the two-paddle design. Also, when many blends are required, the length of the static mixer becomes cumbersome (up to twenty centimeters long, one-quarter of an inch or three eighths of an inch in diameter). This causes a considerable amount of wasted material and also reduces work efficiency.
Thus, there is a need in the industry for a mixing element for a static mixer which can provide better blending of all types of fluids, including highly viscous fluids, so that the length of the static mixer becomes less cumbersome and less material is wasted.
The above-discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by the method for making a multi-paddle mixing element for a static mixer of the present invention.
The method of making the multi-portion static mixer includes providing a split die set having a first die and a second die in axial alignment. Each of the dies has an opening forming an extrusion pattern that mates with the other die. The first and second dies are rotated so that the extrusion patterns are aligned. Extrusion material is extruded through the first and second dies. The first and second dies are rotated simultaneously during the extrusion. The first and second dies are rotated to a misaligned position. The method may also include varying the rate of extrusion during the rotation of the first and second dies to a misaligned position. Alternatively, the extruded material may be rotated as the dies are aligned in a stationary position with one of the dies rotating to a misaligned position to create a space along the shank between mixing portions.
The above description and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following description.